The present invention relates to aircraft, and in particular to semi-buoyant and lighter-than-air aircraft.
Airships are one type of lighter-than-air (LTA) craft. LTA craft utilize small molecular gases (such as helium or hydrogen) or hot air to generate lift.
The lifting gas is contained in an envelope or gas bag. The envelope is typically made of laminated fabrics and other materials such as urethane and rubber. One problem with conventional envelopes is leaking of the lifting gas by way of migration through the envelope walls. Some manufacturers of LTA craft make their own envelopes utilizing proprietary compositions and techniques. These envelopes tend to be expensive and also heavy. In addition, the lifting gases that are contained inside the envelope are carefully controlled to be at or near atmospheric pressure in order to reduce leakage.
The lower pressures of the lifting gas in the envelope also limits the air speed attainable by an LTA craft. This is because at relatively high air speeds, the forward nose of the craft experiences xe2x80x9cdimplingxe2x80x9d, wherein the nose is pushed into a concave form by the wind load. One type of LTA craft is a blimp, which utilizes a cigar-shaped envelope. The nose on a blimp uses battens in order to stiffen the nose, but such devices still do not allow relatively high air speeds.
Furthermore, many conventional LTA craft must often discharge lifting gas in order to land and to change altitude. For example, Nott, U.S. Pat. No. 6,182,924, teaches a ballast control method for an airship by means of onboard tanks of compressed liquefied lifting gas that are expelled into the airship through a heat exchanger. Nott relies on an onboard supply of liquefied lifting gas for ballast adjustment, but also requires the subsequent purging of the gas for descent control. Consequently, these LTA craft have an airborne endurance of only a few hours. When the craft is on the ground, the helium supply must be replenished.
Furtherstill, changes in solar heating upon the envelope causes changes in lifting gas pressure. For example, if the craft begins operation during the night, daylight heating causes the pressure of the lifting gas to increase. Consequently, conventional LTA craft may not be able to maintain flight through a daylight-to-darkness cycle.
Still another problem experienced by conventional LTA craft is landing and subsequent mooring to a fixed mast or anchoring system. The mast or anchoring system is unique to the particular craft. Because of the uniqueness of the anchoring system and the need for a supply of lifting gas, landing facilities for LTA craft can be expensive.
Some additional prior art patents are McMasters, U.S. Pat. No. 3,321,156, which teaches a discoid shaped airship augmented by a buoyant gas in a toroidal gas bag surrounding a centrally disposed engine having an upward facing inlet and a downward facing outlet. The engine is gimbaled for tilting motion relative to the vertical axis. Eshoo, U.S. Pat. No. 4,326,681, teaches a saucer or disc-shaped flexible airship augmented by buoyant gas contained in a plurality of chambers surrounded by an annular pressurized tube and symmetrically disposed around a central chamber, which can be charged or discharged with hot air to allow manipulation of vertical movement. Eshoo also teaches a saucer or disc-shaped flexible airship showing an inflatable annular tube intended to provide a horizontal structural component for the shape of the craft where the vertical forces are transmitted through the central chamber. Henry, U.S. Pat. No. 5,755,402, teaches an airship of nearly neutral buoyancy, toroidal in shape, and with a centrally located downward facing engine thrust, from which thrust is directed by a gate valve arrangement into a manifold of ducts that discharge at the periphery of the aircraft to maintain horizontal and vertical movement.
It is an object of the present invention to provide an airship that minimizes the need for service and replenishment of lifting gas.
It is another object of the present invention to provide an airship that controls vertical flight without venting lifting gas.
It is a further object of the present invention to provide an airship that is easily and inexpensively controlled.
It is a further object of the present invention to provide an airship that can attain high speeds.
The present invention provides an airship that comprises a gas bag for containing lifting gas. The gas bag is located within an outer envelope. There is provided a reservoir of compressed lifting gas, with the reservoir being in selective communication with the gas bag. A compressor compresses the lifting gas from the gas bag and provides it to the reservoir. A controller moves the lifting gas from the reservoir to the gas bag.
In accordance with one aspect of the present invention, the reservoir comprises a hollow ring located around the gas bag. The ring is coupled to the envelope. The ring supports a deck located below the gas bag.
In accordance with another aspect of the present invention, the deck comprises a propulsion unit and vertical and horizontal flight control surfaces.
In accordance with still another aspect of the present invention, there is provided means for providing a suction between the deck and the ground for landing.
In accordance with still another aspect of the present invention, the envelope comprises a flexible sheet material.
In accordance with still another aspect of the present invention, the airship comprises a rigid frame located below the gas bag. An expandable diaphragm is located between the rigid frame and the gas bag. An air injector expands the diaphragm and compresses the gas bag.
In accordance with still another aspect of the present invention, there is provided means for changing the shape of a top of the flexible envelope.
The present invention also provides an airship comprising a gas bag for containing lifting gas. The gas bag is located within a flexible envelope. A compression ring is located around the gas bag, with the ring being coupled to the envelope so as to support lifting loads produced by the gas bag on the envelope. A deck is located below the gas bag with the deck being coupled to the ring by the envelope so as to be supported by the ring.
In accordance with one aspect of the present invention, the deck comprises a propulsion unit and vertical and horizontal flight control surfaces.
In accordance with another aspect of the present invention, there is provided a rigid frame located below the gas bag and above the rigid deck. An expandable diaphragm is located between the rigid frame and the gas bag. An air injector provides air into the diaphragm for expanding the diaphragm and compressing the gas bag.
In accordance with still another aspect of the present invention, there is provided means for providing a suction between the deck and the ground for landing.